This invention relates generally to communications systems, and more specifically to combining signal images in accordance with signal-to-noise ratios.
Signal images from multiple receivers may be combined to determine content included in the signal images. Known techniques for signal combining, however, may require strict gain and noise conditions. For example, the Granlund technique requires signal images with matched gain and noise in order to optimally combine the signal images. Consequently, known techniques for signal combining are unsatisfactory for many needs.
In accordance with the present invention, disadvantages and problems associated with previous techniques for combining signal images may be reduced or eliminated.
According to one embodiment of the present invention, combining signal images includes receiving signal images and performing the following to yield a weighted sum for at least one signal image. A phasor is generated from a signal image in accordance with a correlation reference, and a phase alignment of the signal image is adjusted to yield an adjusted signal image. A signal magnitude estimate is determined in accordance with the phasor, and a weight is determined in accordance with the signal magnitude estimate, where the weight reflects a signal-to-noise ratio of the signal image. The weight is applied to the adjusted signal image to yield a weighted sum for the signal image. The weighted sums are combined to yield a combined signal output.
Certain embodiments of the invention may provide one or more technical advantages. A technical advantage of one embodiment may be that signal images are combined in accordance with the signal-to-noise ratios associated with at least one signal image, such that maximal ratio combining gain may be substantially realized. Accordingly, receiver amplifiers are not required to be matched with respect to gain and noise figure in order to optimally combine the signal images.
Certain embodiments of the invention may include none, some, or all of the above technical advantages. One or more other technical advantages may be readily apparent to one skilled in the art from the figures, descriptions, and claims included herein.